本論文選用溶膠凝膠以及旋轉塗佈法製備氧化鐵半導體的光電極，應用於光電化學產氫系統，嘗試摻雜白金於半導體薄膜中，期望製作出高光電流與高光電轉換效率的薄膜電極。α-氧化鐵擁有2.2eV的低能隙氧化物，能夠吸收波長564nm以下的能量，此波長範圍的能量約佔太陽能量中的30％，吸收範圍包含可見光和紫外光，又因為氧化物有極佳穩定性，可以抵抗光曝曬和化學的腐蝕，符合長久使用。而溶膠凝膠法調配前驅物可降低成本並且製作過程方便，以旋轉塗佈製備出氧化鐵薄膜。本研究嘗試改變旋轉塗佈的轉速、熱處理溫度和氣氛、和白金的摻雜量，以探討出製備的氧化鐵光電極的結晶結構、光學性質、和光電化學性質。由XRD和XPS檢測可得知，在空氣和氧氣熱處理溫度為500℃有α相氧化鐵結構，在波長550nm時，吸收率可達到50%，間接能隙約為2.02 eV、2.00eV；在光電化學反應下，電解液為K2SO3施加偏壓為0.5V，光暗電流差為0.50mA/cm2、0.37 mA/cm2。摻雜白金於氧化鐵薄膜，有提升氧化鐵的結晶性，由XRD和SEM得知晶粒大小有明顯下降，間接能隙為1.98-2.03eV；當摻雜量0.1at%白金，在偏壓為0.5V時，光暗電流差為0.70 mA/cm2。 In this study, the sol-gel and spin coating methods are used to prepare α-Fe2O3 thin film that is used as a photoelectrode for photoelectrochemical (PEC) production of hydrogen. Effects of platinum (Pt) doping are also studied. α-Fe2O3 has a narrow band gap of 2.2eV; it can absorb solar insolation of wavelength smaller than 564 nm, which accounts for approximately 30% of solar insolation. Furthermore, α-Fe2O3 is a stable oxide. It has a good resistance against light exposure and chemical corrosion, and therefore it has a long lifetime. The sol-gel method is a simple and low-cost method for precursor preparation. The resulting gel is deposited on FTO by spin coating. In this study, the effects of spin rate, heat treatment temperature and atmosphere, and the doping amount of Pt in iron oxide on the crystal structure, morphology, optic property, and PEC performance are investigated. The results of XRD and XPS show that α-Fe2O3 can be obtained using 500oC annealing in air or oxygen. At 500 nm, the iron oxide film has a thickness of 228 nm, a band gap of 2.02 eV, and an absorptance of 50 %. As for the PEC performance, the measured photocurrent density is 0.50 mA/cm2 for the undoped iron oxide film with a bias voltage of 0.5V(V vs. Ag/AgCl). Doping of Pt can enhance the crystalline of iron oxide. Increasing the Pt amount reduces the grain size and band gap. With a bias voltage of 0.5V(V vs. Ag/AgCl), the photocurrent density is 0.7 mA/cm2 for the 0.1%-Pt-doped film.
